It is common for a pair of complementary headlights to be provided in high performance road vehicles, or those in the middle of the performance range, being incorporated for example in the front shield panelling of the vehicle. Usually they consist of long range headlights or fog-lights. It is usual to design one type of complementary headlight that will be standard for various different types or models of vehicles, by arranging the means for mounting the headlight on the vehicle so that they can be adapted as easily as possible to different vehicle types. In this connection it is necessary to equip this type of headlight with means for adjusting the beam, in particular on site, because after being fitted on the vehicle, headlights are likely to have different orientations according to the particular vehicles in which they are fitted.
This adjustment is usually obtained by using appropriate adjusting means to tilt the assembly consisting of the reflector and the lamp (light source), the lamp being fixed with respect to the reflector. The purpose of the adjustment is of course to set the light beam at a suitable height. One disadvantage of this known arrangements is that in order to close the headlight sealingly while at the same time enabling a defective lamp to be replaced, it is necessary to close the posterior part of the housing of the headlamp with a trap for giving access to the lamp. This trap constitutes an additional component which increases the selling cost of the unit.
In addition, it is the reflector, which is made of a synthetic material more expensive than the housing, that has to include particular arrangements for mounting the lamp on the reflector, and these arrangements may occupy a substantial volume.
Finally, the lamp and the lamp carrier are quite heavy, and their weight must be supported by the reflector, so that the latter therefore has to be designed to take this into account, with suitable reinforcement, and therefore further material, will be included if necessary.
The amount of possible displacement of a lamp together with its reflector, for adjustment purposes, is conventionally restricted by the fact that no off-set in the position of the lamp with respect to the reflector, outside normally acceptable tolerances, is regarded as desirable by workers in this field.
The adjusting means in the prior art conventionally include a member which can be maneuvered either manually or electrically to cause the reflector, carrying the lamp, to tilt about an axis within a range of angles defined by end-stop abutments carried either by the reflector itself or by the adjusting member. One disadvantage of this known type of adjusting device is that a clumsy or incompetent operator will run the risk, when an end-stop abutment is encountered without satisfactory adjustment having been achieved, of forcing the adjusting member so as to cause irreversible deformation to the component that defines the end stop, or even purely and simply its rupture.